When carrying out repair work on cylinder heads with leaky valves, lapping or replacing the valves and valve seats is not enough. In addition, it is imperative to check the wear of the valve guides. This is especially important to do on engines that have high mileage. Worn guide bushings do not center the valves, which causes high oil consumption. If the wear is high, the riveted guide bushings should be replaced (work must be done at a service station).
Remove valve.
Clean the guide bush with a cylindrical brush.
Insert the valve into the guide sleeve from the side of the combustion chamber and check its play when the valve is moved laterally in both directions.
Attach a steel ruler to check. Backlash should not exceed 0.8 mm; on models 316i from September 1988 and 318i from September 1987 - 0.5 mm.
If required, replace guide bushings riveted (work must be done at a service station).